Heat-insulating units for refrigerator cabinets



June 7, 1960 E. F. DILLON 2,939,311

HEAT-INSULATING UNITS FOR REFRIGERATOR CABINETS Filed March 25, 1957 rIIIIIIIIIIIIIIII'A 2 6.45 CHARGE MIXTURE INVENTOR. Eugene F 17/7/00HEAT-INSULATING UNITS FOR REFRIGERATOR CABINETS Eugene F. Dillon,Chicago, 111., assignor to General Electric Company, a corporation ofNew York Filed Mar. 25, 1957, Ser. No. 648,376

3 Claims. (Cl. 154-45) The present invention relates to heat-insulatingunits for refrigerator cabinets, or the like.

It is a general object of the invention to provide a heat-insulatingunit of deformable pillow-like construction and adapted to be conformedto the space disposed between the inner and outer metal walls of arefrigerator cabinet, or the like, wherein the unit is of improvedconstruction and arrangement including an hermetically sealed bag havingdeformable sheet-like walls of low thermal conductivity that are highlyimpervious to gas J and containing both a deformable mass of poroussolid heat-insulating material and a charge of gas at substantiallyatmospheric pressure, and wherein the charge of gas has a thermalconductivity lower than that of air and essentially comprises a mixtureof carbon dioxide and dichloride-difluoromethane.

Another object of the invention is to provide an improvedheat-insulating unit of the character described, wherein the charge ofgas mentioned essentially comprises by weight about 15 to 25 partscarbon dioxide and about 75 to 85 parts dichloro-difluoromethane.

Further features of the invention pertain to the particular arrangementof the elements of the heat-insulating unit, whereby the above-outlinedand additional operating features thereof are attained.

The invention, both as to its organization and principle of operation,together with further objects and advantages thereof will best beunderstood by reference to the following specification taken inconnection with the accompanying drawing, in which:

heat-insulating unit, taken in the direction of the arrows along theline 44 in Fig. 3; and

Fig. 5 is a greatly enlarged fragmentary horizontal sectional view ofthe heat-insulating unit, taken in the direction of the arrows along theline 55 in Fig. 3.

Referring now to Figs. 1 and 2 of the drawing, there is illustrated acabinet for a household refrigerator, or the like, embodying thefeatures of the present invention and comprising a metal outer shell 11and a metal inner liner 12, both of box-like form, the metal inner liner12 being arranged in nested relation within the metal outer shell 11.The cabinet 10 comprises a portion ofa housea hold refrigerator, aspreviously noted, and cooperates with a refrigerating machine, notshown, that includes a refrigerant evaporator that is operativelyassociated with a food storage space 13 defined within the inner liner12. For example, the refrigerant evaporator may be United States Patent0 2,939,811 Patented Jun e 7, 1960 ICE arranged in any suitable mannerwithin the storage space 13 for the purpose of efiecting the requiredcooling of the food, or the like, stored therein. A substantiallyrectangular heat-insulating frame strip 14, usually formed of a suitablemolded plastic material, is arranged about the open front of the cabinet10 and joining the boundary edges of the outer shell 11 and the innerliner 12. As shown in Fig. 2, the boundary edges of the walls of theouter shell 11 may be provided with inturned flanges and the boundaryedges of the walls of the inner liner 12 may be provided with outturnedflanges, which flanges are joined together by the frame strip 14 inorder to close the space between the shell 11 and the liner 12, thesecuring means for the frame strip .14 being entirely conventional.

Arranged within the space defined between the outer shell 11 and theinner liner 12 are a number of heatinsulating units 20 of pillow-likeconstruction; which heating units 20 are designed nicely to fit betweenthe outer shell 11 and the inner liner 12 and substantially completelyto fill up the space disposed between the elements 11 and 12. Forexample, the space between the outer shell 11 and the inner liner 12 maybe nicely filled by a pair of cooperating and differently constructedones of the heat-insulating units 20, a first of these heat-insulatingunits being deformed into a substantial U shape and arranged to fill thetop and side portions of the space noted, and a second of theseheat-insulating units being deformed into a substantial L shape andarranged to fill the bottom and rear portions of the space noted.

Referring now to Figs. 3 to 5, inclusive, of the drawing, theheat-insulating unit 20 there illustrated is of substantiallypillow-like form and of substantially rectangular configuration; theunit 20 comprising a pair of complementary sheets 21a and 21b disposedon opposite sides of a hat or mattress 22 of heat-insulating material;which sheets 21a and 21b are drawn down snugly around the mattress 22and sealed about the meeting marginal edges thereof, as indicated at 23,thereby to define an hermetically sealed bag confining the mattress 22.Accordingly, the hermetically sealed envelope or bag of the unit 20comprises the two complementary sections of substantially rectangulardish-like configuration and including the pair of opposed facing wallsrespectively defined by the pair of sections and the connecting marginalwall jointly defined by the pair of sections.

In the arrangement, the sheets21a and 21b are formed of deformablesheet-like synthetic plastic material of low thermal conductivity andpreferably of the synthetic organic resin known as Saran, essentiallyincluding poly mers of vinylidene chloride. This material isparticularly recommended because of its resistance to passage of gastherethrough, flexibility, tensile strength, resistance to aging andresistance to chemical attack by a wide variety of chemical compounds.Other satisfactory and reasonably equivalent materials of which eitheror both of the individual sheets 21:: and 21b may be formed are:polyvinyl chloride, vinyl-nitrile rubber, polyethylene, etc., as well.as copolymers of such materials. ,The mattress 22. preferably comprisesa deformable porous mass of solid heat-insulating material, and while itmay comprise a wide variety of such materials, it preferably comprisesamass of loosely packed glass fiber, the glass fibers being suitablymatted to render the hat or mattress 22 sufliciently self-supporting andintegrated .to accommodate ready handling thereof.

Other substances which may be confined in the envelope of the unit 20may include mineral wool, expanded slag, expanded vermiculite, etcf t 7Further, the bag of theuniti20 comprises, a charge (indicated by thereference character 24) of gas in the a p w 2,939,811

form of a mixture of carbon dioxide and dichlorodifluoromethane, andessentially comprising by weight about 15 to 25 parts carbon dioxide andabout 75 to 85 parts dichloro-difluoromethane. Preferably, the mixtureof the charge 24 comprises by weight about 20 parts of CO and about 80parts of CCl- F The charge 24 of gas permeates the bat 22, whereby themattress 22 and .the temperature of the refrigerated space 13 may be aslow as 30 F., whereas, when the refrigerator cabinet is not in use andis involved in railway transportation or in warehouse storage, thetemperature of the space 13 may be as high as +l50 F.; whereby thecharge 24 of gas confined within the bag of the unit 20 may be subjected to any temperature within the so-called operat ing temperaturerange extending from about 30 F.

to about +150 F. Thus hereinafter the expression: operating temperaturerange of the charge 24 of gas confined within the bag of the unit 20refers to the total temperature range to which it may be subjected andnot merely to the temperature range involved in the normal operation ofthe refrigerator cabinet in use. The walls of the bag of the unit 20have suificient elasticity that the normal operating pressure range ofthe charge 24 of gas confined therein in the normal operatingtemperature range thereof (-30 F. to +150" F.) does not departmaterially from atmospheric pressure. Specifically, the walls of the bagof the unit 20 are capable of the necessary distention to accommodatethe required expansion of the confined charge 24 of gas as thetemperature thereof is increased within the normal operating temperaturerange of the unit 20. Ar:-

' cordingly, the bag of the unit 20 is not ruptured, punctured orsubjected to undue strain, within the normal operating pressure range ofthe confined charge 24 of gas in the normal operating temperature rangethereof.

When the unit 20 is in place in the refrigerator cabinet 10, it nicelyfills the space between the cabinet walls 11 and 12; and in placing theunit 20 in this space, it is deformed to conform to this space, themattress 22 and the walls 210 and 21b accommodating the requireddeformation. In the operation of the unit 20, the mattress 22 of glassfibers breaks up the charge 24 of gas confined in the bag thereof, so asto minimize or prevent substantial convection currents within the bag.In the construction of the unit 20, each wall of the bag thereof issubstantially impervious to the passage of air, gas, moisture, etc.,therethrough, and the meeting marginal portions of the two sheets 21aand 21b may be electronically or adhesively sealed, as indicated at 23,so as to provide a complete union between these two sheets.

Heretofore, it has been noted that the walls of the hermetically sealedbag of the unit 20 are substantially impervious to the passage of air,gas, moisture, etc., therethrough by virtue of the construction thereof;and while this statement is essentially correct, these Walls necessarilyhave some permeability with respect to the gases involved, since thesewalls inherently comprise diaphragms through which there is diffusion ofthese gases. In other words, over an extended time interval (6 months to2 years) the difiusions noted become readily measurable; whereby someair from the outside has diffused through the walls into the interior ofthe hermetically sealed bag, and some of the mixture of the gas from theinside has diffused through the walls to the exterior of thehermetically sealed bag.

Now in the event the charge confined in the bag consists; substantiallyentirely of dichloro-difluoromethane, it will be found thatsubstantially all of the diifusions noted are inwardly directed, so thatthere is a slight increase in pressure, above atmospheric pressure,within the hermetically sealed bag, since the walls thereof areconsiderably less impervious to air than to'dichlorodifluoromethane. Onthe other hand, in the event the charge confined in the bag comprisesthe previously mentioned mixture of carbon dioxide anddichloro-difiuoromethane (about 20% by weight CO and about by weight CCIF it will be found that the inwardly directed diffusions and theoutwardly directed difiusions are substantially balanced, so that thereis little or substantially no change in the pressure within thehermetically sealed bag, since the walls thereof are about equallyimpervious to air and'to car-bon dioxide. Now these phenomena pertain topartial pressure considerations involved in the action of thesepermeable diaphragms, andit will be appreciated that when the desireddiffusion balance is achieved, undesirable inflation of the hermeticallysealed bag with air is avoided. In turn, this desired diffusion balanceif substantially achieved when the permeability of the diaphragm tocarbon dioxide approaches the permeability thereof to air, as thepermeability thereof to CCl F may be neglected, so that the outwardlydirected permeation of the diaphragm by carbon dioxide compensates, atleast in part, the inwardly directed permeation of the diaphragm by air.Now, of course, the rate of permeation of the carbon dioxide from theinside of the bag toward the outside thereof, or from the high partialpressure side of the diaphragm toward the low partial pressure sidethereof, gradually declines as the quantity of carbon dioxide in themixture contained in the bag is gradually reduced; however, anobjectionable unbalance is not reached, employing the construction ofthe unit 20 described, in a time interval of at least 20 years, whichtime interval is substantially in excess of the expected useful life ofthe refrigerator cabinet 10.

In the manufacture of the unit 20, the two plastic sheets 21a and 21bare brought together and electronically sealed (or adhesively sealed) atthree of' the boundary edges thereof to produce a sack-like structure,open at one end thereof. The composite hat or mattress 22 is then placedinto the interior of this sack-like structure, and the assembly isplaced in a suitable processing chamber that is then closed andappropriately evacuated in order to subject the interior of the bag andthe composite mattress to a sub-atmospheric pressure, so as to'eliminatetherefrom substantially all of the air and the moisture. Thesub-atmospheric pressure condition in the processing chamber may bemaintained for an. appropriate short time interval in order to insuresubstantially complete removal of the air from the interior of the bagand the mattress. Thereafter gaseous carbon dioxide is introduced intothe interior of the bag and flushed through the mattress so as to purgethere from occluded air, particularly from the surfaces of the glassfibers of the mattress. Thispurging action is continued for a short timeinterval, and during the action the pressure in the processing chambermay be elevated somewhat above atmospheric pressure, and then laterreduced back substantially to atmospheric pressure. At the conclusion ofthe purging action with carbon dioxide, the processing chamber isevacuated so as to remove therefrom a preponderance of the gaseouscarbon dioxide, and so that a controlled amount or residuum of thecarbon dioxide remains in the porous mattress 22. This subatmosphericcondition is maintained in the processing chamber for a short timeinterval; and of course, the amount of gaseous carbon dioxide remainingin the mattress 22 at the conclusion thereof is dependent both upon thesubatmospheric pressure employed in this step and to the time durationthereof. At the conclusion of this step,

aseaerr gaseous dichloro-difiuoromethane is introduced into theprocessing chamber so as to complete the fill of the mattress 22 and thesack-like structure previously mentioned. When the pressure within theprocessing chamber is elevated to atmospheric pressure, there results acharge of gas therein essentially comprising a mixture of carbon dioxideand dichloro -difluoromethane. At this time, the remaining boundary edgeof the sack-like structure is sealed electronically or adhesively, whilethe assembly is in the processing chamber, so as to produce thehermetically sealed bag of the unit 20. Then the process chamber isopened to accommodate the removal therefrom of the finished unit 20.

In the foregoing description of the method of manufacture of the unit20, it was explained that the composite mattress 22 was first introducedinto the sacklike strucutre and then subjected to the purging action ofthe gaseous carbon dioxide, and while this is considered to be thepreferred and normal sequence of the steps, it is noted that it isentirely satisfactory to reverse the order of these steps in the method.Specifically, the composite mattress 22 may be subjected to the purgingaction of the gaseous carbon dioxide prior to the introduction thereofinto the sack-like structure mentioned. More particularly, followingpurging of the mattress 22 with gaseous carbon dioxide, the same may betransferred to storage in an atmosphere of carbon dioxide, and thensubsequently removed from storage and placed in the sack-like structurein the previously described processing chamber. At this time, furtherpurging of the assembly with gaseous carbon dioxide in the processingchamber may be effected, if desired.

in view of the foregoing description of the method of manufacture of theunit 20, it will be understood that the charge confined in thehermetically sealed bag inherently comprises a mixture of CO and CCI Fand that the ratio therebetween may be readily controlled and preset bypreselection of the subatmospheric pressure to which the processingchamber is subjected, following the purging step with CO and precedingthe introduction thereinto of CCl F Specifically, the lower thissubatmospheric pressure is selected, the smaller will be the amount ofCO in the ultimate charge of gas confined in the hermetically sealed bagof the unit 20.

tween the cabinet walls 11 and 12 for the insulating purpose.

In the present construction of the improved heatinsulating unit 20, athermal conductivity (k) is obtained that has a value of about 0.12B.t.u.' per hour per square foot per inch of thickness per F.; whereascorkboard has a corresponding value of k of 0.33 and expandedvermiculite has a corresponding value of k of 0.48. Thus the thermalconductivity of the improved heat-insulating unit Zti is only about /3of that of these good heat-insulating materials named that arefrequently used in refrigerator cabinets; whereby the substitution ofthe heatinsulating units 2.0 of the present invention renders itfeasible to reduce by about /2 the normal spacing between the outershell 11 and the inner liner 12 of the refrigerator cabinet so asmaterially to increase the useful volume of the refrigerator space 13Within the inner liner 12, utilizing the outer shell 11 of givendimensions. Moreover, the weight of these heat-insulating units 20 issubstantially less than that of conventional units thereby effecting acorresponding reduction in the overall weight of the composite householdrefrigerator.

Furthermore, the method of manufacture of the improved heat-insulatingunit 20 involves a minimum number of simple and economical steps thatmay be readily carried out and that are inherently productive of theheatinsulating unit of the construction described.

In View of the foregoing, it is apparent that there has been provided aheat-insulating unit of improved construction and arrangement for readyincorporation into a refrigerator cabinet in the space between the metalouter shell and the metal inner liner thereof, thereby accommodating asubstantial reduction in the wall thickness of the cabinet between theouter shell and the inner liner thereof and contributing materially tocompactness and reduction in the Weight of the cabinet.

While there has been described what is at present considered to be thepreferred embodiment of the invention,

it will be understood that various modifications may be made therein,and it is intended to cover in the appended claims all suchmodifications as fall Within the true spirit and scope of the invention.

What is claimed is:

1. A heat-insulating unit of deformable pillow-like construction andadapted to be conformed to the space disposed between the inner andouter walls of a refrigerator cabinet; said unit comprising anhermetically sealed bag having deformable sheet-like walls of lowthermal conductivity that are highly impervious to gas, a de-' formableporous mass of solid heat-insulating material confined within said bagand generally filling out the volume thereof, and a charge of gas atsubstantially atmospheric pressure confined within said bag andcompleting the fill thereof and thoroughly permeating said porous massof solid heat-insulating material; said charge of gas having a thermalconductivity lower than that of air and essentially comprising by weightabout 15 to 25 parts carbon dioxide and about to partsdichlorodifluoromethane so that there is a substantial balance betweenthe diifusions in opposite directions of carbon dioxide and of airthrough said walls at atmospheric pressure.

2. The heat-insulating unit set forth in claim 1, wherein each of saidwalls of said bag comprises a sheet of synthetic organic resin includingpolymers of vinylidene chloride, and said deformable porous mass ofsolid heatinsulating material essentially comprises a bat of glassfibers.

3. A heat-insulating unit of deformable pillow-like construction andadapted to be conformed to the space disposed between the inner andouter walls of a refrigerator cabinet; said unit comprising anhermetically sealed bag having deformable sheel-like walls of lowthermal conductivity that are highly impervious to gas, each of saidWalls of said bag including a sheet of synthetic organic resin, adeformable porous bat of glass fibers confined within said bag andgenerally filling out the volume thereof, and a charge of gas atsubstantially atmospheric pressure confined within said bag andcompleting the fill thereof and thoroughly permeating said porous bat;said charge of gas having a thermal conductivity lower than that of airand essentially comprising by weight about 15 to 25 parts carbon dioxideand about 75 to 85 parts dichloro-difluoromethane so that there is asubstantial balance between the dilfusions in opposite directions ofcarbon dioxide and of air through said walls at atmospheric pressure.

References Cited in the file of this patent UNITED STATES PATENTS1,942,162 Campbell Jan. 2, 1934 2,067,015 Munters Jan. 5, 1937 2,649,101Suits Aug. 18, 1953 2,779,066 Gaugler et a1 Jan. 29, 1957 2,817,123Jacobs Dec. 24, 1957 2,824,364 Bovenkerk Feb. 25, 1958

1. A HEAT-INSULATING UNIT OF DEFORMABLE PILLOW-LIKE CONSTRUCTION ANDADAPTED TO BE CONFORMED TO THE SPACE DISPOSED BETWEEN THE INNER ANDOUTER WALLS OF A REFRIGERATOR CABINET, SAID UNIT COMPRISING ANHERMETICALLY SEALED BAG HAVING DEFORMABLE SHEET-LIKE WALLS OF LOWTHERMAL CONDUCTIVITY THAT ARE HIGHLY IMPERVIOUS TO GAS, A DEFORMABLEPOROUS MASS OF SOLID HEAT-INSULATING MATERIAL CONFINED WITHIN SAID BAGAND GENERALLY FILLING OUT THE VOLUME THEREOF, AND A CHARGE OF GAS ATSUBSTANTIALLY ATMOSPHERIC PRESSURE CONFINED WITHIN SAID BAG ANDCOMPLETING THE FILL THEREOF AND THOROUGHLY PERMEATING SAID POROUS MASSOF SOLID HEAT-INSULATING MATERIAL, SAID CHARGE OF GAS HAVING A THERMALCONDUCTIVITY LOWER THAN THAT OF AIR AND ESSENTIALLY COMPRISING BY WEIGHTABOUT 15 TO 25 PARTS CARBON DIOXIDE AND ABOUT 75 TO 85 PARTSDICHLORODIFFUOROMETHANE SO THAT THERE IS A SUBSTANTIAL BALANCE BETWEENTHE DIFFUSIONS IN OPPOSITE DIRECTIONS OF CARBON DIOXIDE AND OF AIRTHROUGH SAID WALLS AT ATMOSPHERIC PRESSURE.